Aviation trainer



Sept. 1,2, 1944. G. LowKRANTz Y AVIATION TRAINER Filed vJune 29 1942 wv .3. mm. o9

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I N V EN TOR. GUNNE OWKRANTZ /J ATTORNEY Patented Sept. 12, 1944 AVIATION TRAINER Gunne Lowkrantz, Bnghamton,`N. Y., assignor to Link Aviation Devices, Inc.,-Binghamton,A N. Y., a corporation of New York Application June 29, 1942, Serial No. 448,905

30 Claims.

with an aviation trainer which constitutes essentially a simulated aircraft fuselage mounted upon a universal joint whereby the trainer can be turned, pitched and banked in simulation of a plane in flight. Such a trainer is disclosed in U. S. Patent 1,825,462, United States Patent 2,099,857 discloses means wherebythe functioning of certain of the instruments in an airplane such as the altimeter, vertical speed indicator, and air speed indicator may be simulated in such atrainer.

One of the principal objects of this invention is to provide, in such a trainer, means to be used in connection with the instruments described in the above-mentioned U. S. Patent 2,099,857 whereby the rate of climb or-vertical speed indicator and altimeter may be made to respond more closely in simulation of the functioning of the corresponding instruments in areal plane in flight.

Another principal object of this invention is to provide means which will not permit damage to the Vertical speed indicator and altimeter whenever the climb or dive valve in the trainer is opened in the presence of a high or low pres# sure in the equalizer tank which forms a part of the instrument control mechanism.

Another principal object of this invention is to incorporate in the instrument system of such a trainer means to maintain a constant differential within predetermined limits across the ports 0f the climb and dive valves at all times when the system is in operation.

Other objects and advantages will Abecome apparent `as the description proceeds, reference now being made to the accompanying drawing forming a part of this application and wherein like reference numerals indicate like parts,

In the drawing,

Fig. l is a side view of a trainer in which this invention is particularly useful', certain parts being cut away for purposes of illustration.

Fig. 2 is a diagrammatic illustration of a preferred embodiment of the present invention shown in relation to certain of the parts of such a trainer.

Referring to Fig. 1, it will be seen that such aitrainer comprises a fuselage I0 mounted upon a universal joint designated generally as I2 which in turn rests upon a central supporting member I4. The central supporting member I4 is rotatably supportedin rbase I B. The universal joint I2 and the rotatable mounting of .central support I4 in base rl 6 make it'possiblefor the student in the trainer, by a manipulation of the controls in said trainer, to Apitch and bank said trainer fuselage to any desired position as well as turn the fuselage about its vertical axis. vInasmuch as the base I6 at al1 times remains .stationary the trainer makes no forward orvertical movements. The means for accomplishing the movements of the trainer fuselage I0 are completely disclosed in the two above-mentioned United States patents and, therefore, form no part of the present invention except in combination with the detailed means to be described hereinafter.

It will be realized thatl in an airplane there is provided an altimeter which indicates the height of the plane above some point on the earths surface as well as a rate of climb or vertical speed indicator which shows at any given instant whether the plane is gaining or losing altitude, or whether it is in level flight. In the event that the planeis not in level flight, the rate of change of the altitude of the plane is shown bythe vertical speed indicator. These twoinstruments in a real plane areresponsive to the pressure of the atmosphere which surrounds them, the altimeter being responsive to the' absolute pressure and therefore indicating the eheight of the plane above some point on the earths surface, andthe vertical speed indicator, being responsiverto the I rate of change of the pressure of theatmosphere surrounding it, 'therefore shows the rate of change of the altitude of the plane.

The altimeter in a plane has an indicating hand which moves across the dial a distance proportional to the change in atmospheric pressure, and hence, proportional to the change in the. altitude of the ship. The vertical speed indicator has a hand which remains in the horizontal position when the atmospheric pressure is constant, thus indicating thatv the plane is in level flight, this hand moving upward when the atmospheric pressure is decreasing, and moving Ydownward when the atmospheric pressure isv increasing, thus indicating that the plane is gaining or losing altitude, respectively,

As before stated, the trainerV of the type before mentioned, although. it be in` a climbing or diving attitude does not. actually gain or lose altitude. Nevertheles-s,k it has been found advantageous to installin the trainer. anv altimeterv and a vertical speed indicator to indicatefltheassumed trainer altitude and assumed rate of Vchange of trainer altitude. In order that these instruments in the trainer will properly show the assumed trainer altitude and assumed rate of change of such altitude, an equalizer tank has been installed in the trainer. The altimeter and vertical speed indicator are connected to this tank and by causing the pressure within this tank to change according to the assumedy trainer altitude in the same manner that the atmospheric pressure around a plane in ilight changes asthe altitude of the plane changes, the altimeter and vertical speed indicator inthe trainer will show the assumed trainer altitude and assumed rate of change thereof.- VThis tank, as

shown in U. S. Patent 2,099,857, never has more than the prevailing atmospheric pressure therein the attitude of the ship or throttle settin in, and whenever the trainer is dying at an altitude above that represented by a pressure within the tank equal to atmospheric, the presure within the tank is less than atmospheric,

I nasmuch as the altitude of aplane at a given j moment depends upon'the "successive, attitudes and throttle positions thereof asl well as ,the

length of time that, the plane has maintained its ysuccessive attitudes' and throttle settings since Vthe takeoff, the pressure within the tank in the trainerV at a given moment is lalso made to depend upon these same factors inthe trainer, If the trainer assumes a climbing attitude, the throttle settingremaining constant, the pressure within thertank decreases,.the total decrease dependingupon the angle of climb `and the length of time the trainer remains in its climbing posig tion. The vtotal decrease in pressure within` the tank yaiects, the altimeter which gives the assumed altitude of the trainer. `The rate of decrease at any-given moment, throttle setting not Y considered, will depend upon the attitude of the trainer, ,andV the vertical speed indicator will respond to this factor. Of course-if the trainer assumes a divingY attitude the pressure within the tankjis built unaccording to the same rules and theinstrurnents respond accordingly. n Also, if the throttle in the trainer is opened, the trainer attitude remaining constant, the pressure Within the tank isdecreased, the total decrease 'depending upon the amount' of the opening of the-throttle as wellfas the Ylength of time that theV throttle yremains open. TheV rate of YVchange depends upon the amount that the throt- Atle is opened. The altir'neter and vertical speed indicator will respond appropriately.

The changing of the pressure Within the tank in response toa change, in the attitude of the trainer orto a Changel in the throttle setting thereof, thereby causing a change in the readings of the altimeter and vertical speed indicator, is described in detail and claimed Vin the abovementioned United States Patent 2,099,857. However, in the said patent, if the pressure within the tank were relatively high, and therefore, the trainer were assumedto be flying at a relatively low altitude,'the placing of the trainer in a climbing position or the opening of the lthrottle would Y cause a rapid Vdecrease in the pressure within the tank and the` altimetezzand vertical Yspeed indicator wouldrespond Vexcessively as compared with the responses of the Ycorresponding instrumentsin a real plane to corresponding changes `in .throttle position'or attitude. On the other hand, if the pressure within the tank were relatively low, and'therefore, the trainer were assumedtube flying at a relatively high altitude, a change of the trainer toa diving attitude or a closing of the throttle would cause af'grfi? @111191.41111 therein.

Referring to Fig. 2, vacuum pump i8 is connected by `means of tube 2G to duct 24, the left end of which is in communication with the pressure regulator designated generallyas 26which pressure regulator is associated with the climb valve which is designated generally as 28.V The right end of duct 24 is in communication with the pressure regulator designated generally by 39, and this pressure regulator is associated with 'thefdive valve which in turn is designated generally by the numeral 32. s

Pressure regulator 26 has at one end an expansible metal bellowsr 34, the upper end rof which as viewed in Fig. 2 is rigidly affixed to a suitable frame member (not shown) which supports thel pressure regulators 26 and30. The lower end of the ,bellows 34 has aixed thereto a reciprocable shaft 36 which is free to move back and forth in the housing 38, which housing is rigidly mounted upon the frame member just mentioned. The lower end of shaft 36, as seen in Fig. 2, is rigidly aflixed to the upper end of bellows 40 which is exactly likebellows 34, and the lowe-r endof bellows Y4l) is-also rigidly affixed to said frame member. It' will be noticed that the central `part 42 of reciprocable shaft 36 is greatly reduced in diameter to form a valve. Housing 38, which housing completely surrounds shaft 3%, has a central port 44'and when said shaft Sii is in its central position, port 44 is in commu'nication with the space around the reduced central Vport 52 which communicates with previously mentioned ducty 24 and on the. oppositeV side of port 44 is a third port 54 which is in communication with the atmosphere.

When reciprocable shaft 36 is in its central position port 44 is not in communication with either port 52 which leads to the source of reduced air pressure I8 or Vwith port 54 which leads to the atmosphere. Howeveryin the event that reciprooable vshaft 36 is moved toward the f bellows 34, port 44, by virtue of the central" valve 42, will communicate with port 52 which leads to the source of reduced air pressure, but port 44 will not communicate with the port 54 which leads tothe atmosphere. In vthe event that member 36 moves in the opposite direction, port 44 will communicate with atmospheric port 54 but will not communicate with reduced air pressure port 52. It will be realized, therefore, that the position of reciprocable member 36 determines whether the port 44, and consequently whether bellows 40 and port 50 of climb valve 28, is in communication with reduced air pressure port 52, atmospheric port 54, or neither of them.

58 is connected to bellows 34 by means of tube 6 2. Spring 64 encircles the upper end of reciprocable member 36 and is interposed between the upper endV of housing 38 and the lower end of bellows 3 4.

Because of the aforedescribed arrangement, the pressure within equalizer tank 58 is at all times equal to that present in the port 56 of climb valve 28 and is also equal at all times to that present in bellows 34. The pressure within bellows 4 0 is at all times equal to that present in the port 50 of climb valve 28. Assuming that the pressure within equalizer tank v5 8 and hence the pressure within port 56 and bellows 34 is less than or equal to the pressure within bellows 40 and hence port 5U, the compression of spring 64 will collapse bellows 34 thereby causing reciprocable member 3 6 to move toward bellows 34 allowing communication between port 44 and reduced airport 52. Vacuum pump I8 will therefore, through tube 20, duct 24, port 52, valve 42, port 44, and connections 46 and 48, be in communication with bellows 40 and, consequently, the pressure within bellows 40 will be reduced. This reduction of pressure within bellows 4I! will tend to collapse that bellows and this reduction will continue until the pressure within bellows 40 and port 50 is less than the pressure within bellows 34 (and therefore witlL'n tank 58and port 56) by an amount equal to the compression of spring 64. When this point is reached, it will be realized that the central valve 42 of reciprocable shaft 36 will have returned to its central position and the' port 44 -will no longer be in communication with reduced air port 52, nor will it communicate with atmospheric port 54. When this condition is realized, inasmuch as the pressure within bellows 4D is less than the pressure within bellows 34 by the amount of the compression of spring 64, the pressure in port 50 of climb valve 28 is less than the pressure in port 56 of climb valve 28 by the same amount. I

The pressure within bellows 34, on the other hand, can never remain more than the pressure within bellows 46 by an amount greater than the compression of spring 64 becausesuch a condition would force reciprocable shaft 36 past its central position toward bellows 40, thereby allowing communication between port 44 andr atmospheric port 54. Atmosp-here would therefore enter bellows 4!) through tube 46 until the pressure within bellows 46 becomes less than the pressure within bellows 34 by an amount only equal to the compression upon spring 64. When this point is reached, reciprocable shaft `36 would again be in its central position.

It is therefore clear that whenever climb valve 28 is closed, regulator 26 will place across the ports 56 and 50 of climb valve 28 a differential equal to the compression of spring 64. Y

Regulator 36 which regulates the pressure across the ports of dive Valve 32 is of thesame general type as the regulator 26 which has just been described, except spring 66 of the dive regulator 30 is on the opposite end-of regulator 30. It will be noticed in Fig, 2 that bellows 63 of regulator 30 is connected to the port 16 of dive valve 32 by means of connections 69 and 1|, and this same bellows is connected by means of the other end of member 1l to the central port 12 of thehousing 14 of regulator 30. The other bellows 'Hi @if regular@ `3l! is cprmeted by means? of tube 62 to the equalizer tank 58. The second Dort 18 of housing 14 is connected to the output of vacuum pump I8 by means of tube 1 9. Relief Valve I3; controlsthe flow of air from the output-cof pump I8 te Dort 18. This valve may be of any suitable type provided it allows to pass into port 18 a pressure constantly above atmospheric slightly in excess of the compression of spring 66. All pressure above this amount is allowed by this valveA to pass into the atmosphere. The third port 8-3 of regulator 36 is connected to duct 2 4; which, as explained before, is connectedv to vacuum pump I8 by means of tube 20. The lower end of bellows 16 is attached to the upper end of shaft which is reciprocable within housing 14, shaft A80 being turned down as shown to form the valve 8l. The lower end of shaft 80 is affixed to the upper end of bellows 68.

Assuming the pressureV within bellows 68 toy be equal to or less` than the pressure within bellows 16, spring 66 will'collapse bellows 68 and reciprocable member 80 will be drawn toward bellows 6 8, valve 8| will allow communication between ports 12 and 18 and, therefore, the pressure of the output of Vacuum pump I8 which is allowed by valve I9 to pass into port 18 will enter bellows 68; by means of connections 1I and 69 until thepressure Within this bellows is greater than. the pressure within bellows 16 by an amount equal to the compression of spring 6 6. At this time, reciprocable member 80 will have returned to its central position.

The pressure within bellows 68 can never remain more than the pressure within bellows 16 by an amount greater than the compression upon spring 66r because such a condition would force reciprocable shaft 80 from its central position toward bellows 16 thereby permitting communication between portsV 83` andv 12. Reduced air pressure would therefore be applied to bellows 68I until the pressure Awithin lthat bellows is reduced tothe point where it exceeded the pressure within bellows 16 by an amount equal to the compression of spring 66. When this point is reached, reciprocable shaft 80 would again bein its central position.

Therefore, the pressure within bellows 68 always becomes greater than the pressure within bellows 16 by. the amount of the compression of spring 66. Inasmuch as the pressure within bellows 16 is equal to the pressure within equalize;` tank 58 and to the pressure within port 82 of diveV valve 32, while the pressure within bellows 68 is always equal to the pressure within port 10 of dive valve 32, it will be realized that the pressure differential between the two ports 10 and 82 of the dive valve 32 will always be equal to the compression of spring 66.

The detailed construction of the climb valve 28 and the dive valve 32 forms no part of the present invention and for. a detailed description thereof reference is made to the above-mentioned U. S. Patent 2,099,857. In order to understand the instant invention, it is sufficient to know that Aeach of the valves 28 and 32 is a,- needle valve, in the case of the climb valve 28 the needle and seat beingv between the port 56 leading to equalizer tank 58 and the port 50 leading to the bellows 40, while inY the case of dive valve 32 the needle and seat are between the port 82 leading to equalizer tank 58 andv port 10 whichk leads to bellows 6 8. Connected integrally with the needle's in each o f the valves is a threaded stern, the outer ends of which are designated by the differential pressure being at all times equal tothe compression upon spring 64 and not aifected `p any change in the pressure differential betwee the equalizer tank 58 and pump I8.

On the other hand, if the throttlein a plane 4is closed, it is well known that the altitude o f lthe ship becomes lower, and the altimeter will reject this decreased altitude while the vertical speed indicator will show the fact of descentandrate thereof. It will be realized thatl avrnovementnto the right in Fig. 2 of throttle I I8 will cause link |36, the lower end of arm |38, member |40 an d reciprocable member Y96 to move to the left in Fig. 2. This movement, as explained above, wil, l not affect climb valve 28 burI will cause dive valve 32 to open,` thereby allowing communica; tionbetween equalizer tank 58 and bellows 68 by means of connection 60 and ports 82 and '1| l. As the pressure in bellows 68 and pjort 18 is Aat all times greater thanthe pressure within bel-4 lowsl 16, equalizer tank 58, and porty V8,2 by an amount equal to the compression upon spring 66, whenever dive valve 32 is openedby move,-v ment to the left in Fig. 2 of reciprocable member 96, which movement may be caused by a closing of throttle II8, air will flow from bellowsA 6,8, through connections 69 and 1I, ports 10 and 8,2

of dive Valve 32 and connection 60 into equalizer Altimeter I |4 will reflect a' decrease in' tank 58. the assumed trainer altitude while vertical speed indicator ||0 will show the fact of assumed' descent Vand rate thereof.

This ow of air from bellows 68 intogequalizer tank 58 and therefore into bellows 16 vwill cause a contraction of bellows 68 and an expansionof bellows 16, `and therefore, reciprocable member 80 of dive regulator 30 will move towards' bellows 68. This movement will allow communication between port 12 and pressure port 18 and,` therefore, air from the output of vacuum. pump I8 will flow through tube ,19' into ,bellows 6,8, causing the same to expand. will continue to` ilow into bellows 68 until the lpressure within that bellows is again higher than the,,pressure within bellows 16 and equalizer ltank 58 by1an.

amount equal to the compression upon spring;

66. When this point is reached, as'much airwill ow through pressure port 18 and `into bellows 68 as is exhausted from this kbellows'through dive' valve 32 by equalizer tank 58.

, Therefore, itV will be realized that wi'ieneinr thev assumed altitude of the trainer is ,decreasingbecause of a closed throttle position thel dilerential pressure across theA portsr of the dive valve 32 will at all times remain constantregardle'ss of the differential between valve I9 and tank' 58;

Whenever a plane in iiight changes its attitude, that is,A its angle of climb or dive, achange in the altitude of the plane results, the altimeter.

reilecting' this change andthe vertical speed indicatorshowing the direction of the change and the rate thereof. The followingr meansare',

incorporated in my inventionto simulate thesei instrument responses.

YAs seen in Fig. 2, horizontal'shaft |42 ism'ouut:

ed for rotation in bracketsr |44, only one'of which is shown, which brackets are xedly attached to the bottom 31 of `the trainer fuselage I0. The left end of shaft |42 has rigidly affixed theretoarm |46 and to the upper end of `this arm is rigidly aiilxedstub shaft |48. To the left endf of stub shaft |48, as before stated, is kpivotally at taclled end ofv shaft |42 nearer universal loint 1.2 has rigidly affixed thereto a lever |50 which is re.-

ferred la ,the ali as the. ,Pitch action take-,aff lever.. the .tirer ieder which has connected aerea anatra of a irrite' 152,. other en@ of spring y|52 s c to member |54 whieh at all times remainsv stationary. The lower end oflever |r has suitably attached theretoha' roller |56, and rigidly aiized to the centralsupport I' 4 ,of ,t he ytl'failler by yrriefai'ls of bolts |58 is an upwardly, extending I 'nenberv |60, referred to in the areas the pitohaotioh oaui, y shown vin Fig. 1, the weight of the, trainer fuselage IQ rests upon the top of universal joint I2 by means lo'f brackets |62,even', though` the bottom 31 of the fuselagefisbelow the universal joint I2. The complete mechariismshownin Fig. 2 .except central support i4, stud y|.f4,1spriiije |52 arid 'eamlsn rests' upon the bottom of the trainer fuselage. Because of, thefact thattl'l'e mecha,- nfi's shown in 2, fxcpt as just stated, ,is suspended b'elovvfuniversal joint yI2 and at the same time itrests upon ...this universal joint,r vit will be understood thatwhen the trainer fuselage lo piteh'e's in' simulation ,of olim'biu'g, yshaft lijf moves ahead. off its level flight positioubut rollerl |56 ariel the lower part Yof lever |50 oaiihot st ihove because oi oath shaft |42 will therefore tu'rrir ih brackets |44 ih a oouhterclockwise directiofn a s` viewed from the left side ofvv ,the trainer, fuselage.V` Astulo' shaft |48 will therefore bemoved ,toward the front of rthe trairerby vthe turning of arm |46, and arm |38 pivot about the' pnt where lihlo lasiis atd toit.l The lower 'end lof ar 1n|,38, will the fjore nieve tothe rear or' to the right in lii'g. 2 astvill member mand' reoiprooable member 96; will causer climb. valve' 28. to open but `the position of dive valve 32 will remain the same.

inasmuch Ias it hasbeeil demonstrated that wheheyeroliihb valve .28 isopehed ty virtue of a veent of thIfttlil' Cllb regulator 2 6. t'all times maintains across-v the. two ports of climbvalve 28 a.V constant diierential equal tov thecompres'sion 1119011 .Spring 64, it is deemedlineSlry t "deI ll,1St '/te thtreglat'l Xper-- fo s the same function Whenever climb valve 2 8 Vsjopened through- 'acha'n'g'e yin the attitude oi the 4trainer vbecause, asseerrih Fig, 2, climb valve 28 is' always opened .by a movement .of reciprocable member Y96,

ywhenever `the trainer isgpitohed ihifsihulatieii of lits 1eve1iii'ght position arid beoausasilrng |42 willl be made toy turn in brackets |44 in a f direojtioh to eausestulo shaft las' to move toward the rear of the trainer. The lower end of arm [ssj will thereioregbe moved toward the head Yof the trainerl 'as will niernberv|40 and reoiprocable member v96, thus kcausirlg dive valve 32 to open, eliihovalve v la remaining. in the closed position. In" L Y l' dive valve. 32I is` 'op' ene`d through a movement o 'throttle II`8, dive re gillator 3U at ,all times ains acr'ossthetwo ports of dive valve 32'.

av eohst'aht'difierehtial pressure equal tothe eoiiii;l

@session of spring 6 6, it is deemed unnecessary h propelling ofthe thrtile andZOl axzlilnbina;

attitude of the fuselage results in a decrease in the pressure within tank 58, while opposite movements of these two controlling elements results in an increase in the pressure within the equalizer tank. VThis pressure governsthev indications of altimeter II4 and vertical speed indicator III), the higher the pressure `the lower the indicated altitude, an increasing pressure causing the vertir cal speed indicator to register the rate ofdescent anda decreasing pressure'causing it 4to register the rate of climb; These two instruments will,

therefore, respond to changes in attitude and throttle setting in the same manner that the correspondinginstruments in a plane in flight would respond to such changes. i

When the trainerA is first set in operation theY pressure within equalizer' tank 58 is equal to atmospheric pressure as is the pressure Awithin bellows V34 and port 56'of climb valve 28. The pressurewithin bellows 40 will become, asexplained above, through the action of regulator,

lessthan atmospheric by an amount equalV to the compression upon spring64. The student, upon first starting his filight, will generally attempt togain altitude. This will be done through an openingY of the throttle II8 (that is, pushing Y it to the left in Fig. 2) as well asthrough placing theY trainer in a climbing position. VBoth'of these movements will, ras explained above, open climbrvalve V28 but will leave dive valve 32 closed. Y In theprior art, without the pressure regulators of this invention, theport 50 of climb valve 28 kwas connected directlyrto vacuum pump I8,

or its equivalent, as described in the same Unitedr States `Patent 2,099,857.A When the pressure withinfequalizer tank 58 was atmosphericor near atmospheric as in the beginning of the ilight, a great and undesirable differential was present across the ports of climb valve 28 and upon the opening ofthe climb valve, as explained above, an excessive amount of air rushed from equalizer tank 58 to vacuum vpump I8.

Thiscondition of excessive rate of fi'ow 'and' instrumentactivityprevailed for a certain length of time until, when the approximate proper pressure differential across the ports Vof the climb valve wasV present,'the rate of ow and 'instru-f ment Vindications were appropriate. Then, how- "ever, the pressure differential became too low and the Vrate of flow and indications' of the in-` strumentsweregradually lessened until the pressurein Vthe equalizer tank 58 was equal to that of thelvacuum pump I8'. 'At this point the absolute ceiling of the trainer,` was reached.

Such a functioning of the vertical speedV indicator and Valtimeter in the trainer came far fromr simulating the functioning of the same instruments in a plane. Ina real plane these instrumentsV would show, with a given attitude land' throttle setting, a more or less steady climb until Vtheservice ceiling was reached, then VaV sharp decrease in the ratejofpclimb until thea'bsoluteceiling wasV reached. Thisis in sharp contrast to therate of climb as shown by theivertical speed indicator and altimeter in the trainers, of

the prior art.

ion the other hand, with the regulator 2s in-V terposed between climb valve t 28 and -vacuum pressure prevailing in` equalizer tankr58, when climb valve 28 Vis opened the ow of air from equalizer tank 58 Vis no greater than if the pressure in tank 58 weremuchless i.e., if the trainer were at a much higher assumed altitude. The

ilow'of air throughA climb valve 28" at. any timethat climb valve 28 may .be 4openedisinclependenter the diirereniieu between tank t8' and vacuum pump I8 (and therefore, is independent of the assumed trainer altitude), until the pressure within tank 58 becomes so low that it does not exceed the pressure within vacuum pump I8 by an amount equal to the compression of spring 64. Hence, up to this point the steady climb of a plane resulting from a given throttle setting and attitudeY will be reflected Iby the altimeter and vertical speed indicator. At this point the service ceiling of the trainer is reached. nWhen' the differential across the ports 56 and 50 of the climb valve becomes less than the compression of the spring 64, the indications of the vertical speed indicator and altimeter will show that thel assumed rate of climb of the trainer is increasingly less until the pressure within equalizer tank pumpv I8,Vwith Vatmospheric vor near atmospheric 58 is equal to that of vacuum pump I8. The absolute ceiling ofthe trainer is then reached. This slower change in the instruments afterV the serviceceiling of the trainer is reached simulates closely the reaction of the same instruments in a real plane after the service ceiling of the plane is reached.

Considering now the functioning of dive regulator `3l), regardless of how great the assumed Y altitude of the trainer becomes, and, therefore, regardless of how low the pressure within equalizer tank 58 becomes, 'dive regulator 3.0 limits the dilerential across thedive valve ports 10 and 82 to an amount equal tothe compression upon spring 66. If the dive regulator 30 were-not provided, port 'I0 would communicate directly with the atmosphere, as shown in United States Patent 2,099,857, and the differential at any given time across the ports "I0 and 82- of dive valveV 32 would be equal to the amount that the pressure within equalizer tank 58 is less than atmospheric. Consequently, if the, trainer was flying at a high assumed altitude, when dive rvalve 32 was opened Van excessive amount of air rushed'into equalizer tank 58. Vertical speed indicator III) showed an assumed rate of descent far in excess 0f the actual performance of a real plane under the conditions-being simulated, altimeter IM reacting in the same manner. In this case, also, damage to the instruments was probable. As the ati mosphere within tank 58 becamev increasedthe rate of flow thereinto whenever dive valve 32 was tude .of the trainer, the differential "across theV ports 'I0 and 82 ofdive valve V32is` equal tothe compression upon spring Y68.V Thejilow of air from bellows `68 into equalizer .tank 58 whenever dive valve 32 isope'n will be independent of the pressurewithn tank 58. *Therefore the reaction of altimeter H4 and'vertical `speed indicator IIIJ will `closely follow the reactions of the same instruments in aplane in flight.-V

As statedearlier in this description, relief valve I8 always allows a pressure in'wtubei'IS and port 'I8 of regulator 30 slightly abovethe sum of the prevailingatmospheric pressurel and the compression of spring 66. VThis being so, even though the pressure withinequalizer tank 58 be nearly atmospheric, the pressure Within bellows 68 will be greater than the pressure within the equalizer tank 58 by an amount equal to the compression of spring 66. This desired differential will remain until the pressure within tank 58 is equal to atmospheric.

With my invention, before a night in the trainer the lowest assumed altitude at which the trainer will ily during that flight is determined. Pump IB is then turned on and immediately there is across the climb and dive valves a pressure differential equal to the compression of springs 64 and 66, respectively. The altimeter H4 is then set to the mentioned lowest assumed altitude and the trainer is then flown till the altimeter indicates the assumed altitude of' the beginning of the flight Thereafter, throughout the whole flight unless the service ceiling of the trainer be exceeded, a differential pressure equal to the compression of the two springs will be maintained across their respective valves.

A bleed hole |64 is provided in relief valve I9, this bleed hole at all times being in communication with tube 19. With this provision when the vacuum pump i8 is shut olf, if the dive valve 28 be left open the pressure within equalizer tank 53 will become atmospheric.

It will be realized, therefore, that with the means disclosed by the preceding description and accompanying drawing, the altimeter and vertical speed indicator in a grounded trainer may be made to respond to a change in throttle setting as well as in the attitude of the trainer in a manner closely approximating the response of the same instruments in a plane in actual flight to the same movements. However, the preceding disclosure is a preferred embodiment only of this invention which may be readily changed in many respects without departing from the spirit and scope thereof. Therefore, I limit myself only by the following claims when construed in View of the prior art,

I claim:

1. In a grounded aviation trainer for the instruction of student pilots the combination of an equalizer tank having a controlled variable pressure potential, a source of lower pressure connected with said tank, avalve interposed between said tank and said source of lower pressure, and means associated with said valve, and operable within predetermined limits, for causing a uniform now from said equalizer tank to said source of lower pressure for a given valve opening regardless of the pressure differential between said tank and said source of lower pressure.

2. In a grounded aviation trainer for the instruction of student pilots, the combination of an equalizer tank having a controlled variable pressure potential, an instrument for indicating assumed altitude changes connected to said tank, said instrument being responsive to the pressure within said tank, a source of lower air pressure connected with said tank, a valve interposed between said tank and said source of lower air pressure, and means associated with said valve, and operable within predetermined limits, for causing. a uniform flow from said tank to said source of lower air pressure for a given lvalve opening regardless of the pressure differential between said tank and said source` of lower air pressure. v

3. In a grounded aviation trainer for the instruction of Student pilots the combination of" an equalizer tank having a controlled variable pres# sure potential, an instrument for indicating assumed altitude changes connected to said tank, said instrument being responsive to the pressure within said tank, a source of lower pressure connected with said tank, a valve interposed between said equalizer tank and said source of lower pressure, and means associated with said valve, and operable within predetermined limits, for causing a uniform flow from said equalizer tank to said source of lower pressure for a given valve opening regardless of the pressure differential therebetween, and within other'predetermined limits a flow dependent upon the pressure differential between said tank and said source of lower pressure.

4, In a grounded aviation trainer for the instruction of student pilots the combination of a throttle, an equalizer tank having a controlled variable vpressure potential, an instrument for in-k dicating assumed altitude' changes connected to said tank, said instrument being responsive to the pressure within said tank, a source of lower pressure connected with said tank, a valve inter- Y posed between said tank and said source of lower pressure, said valve being responsive to the setting of said throttle,'and means associated with said valve, and operable within predetermined limits, for causing a uniform flow from said equalizer tank to said source of lower pressure for a given valve opening regardless of the pressure differential between said tank and said source ofy lower pressure. f

5. In a grounded aviation trainer having a fuselage capable of pitching in simulation of the climbing and diving of a plane in actual flight,Y

the combination of an equalizer tank having a controlled variable pressure potential, an instrument for indicating assumed altitude changes connected to said tank, said instrument being responsive to the pressure within said tank, a source of lower pressure connected with said tank, a valve interposed between said tank and said' source of lower pressure, said valve being ref sponsive to the pitching of said fuselage, and

the combination of a throttle, an equalizer tank having a controlled variable pressure potential, an instrument for indicating assumed altitude changes connected to said tank, said instrument being responsive to the pressure within said tank, a source of lower pressure connected with said tank, a valve interposed between said tank andV said source of lower pressure, said valve being responsive to the pitching of said fuselage as well as tothe setting of said throttle, and means associated with said valve, and operable within predetermined limits, for causing a uniform flow from said equalizer tank to said source of lower pressure for a given valve opening regardless of the pressure dilerential between said tank andY said source of lower pressure.

`7. In a grounded aviation trainer for the instruction of student pilots the combination rofan equalizer tank having a controlled variable pressure' potential, anv instrumentfor indicating as'- sumed `altitude changes connected tc saidY tank',

said instrument being responsive to the pressure within said tank, a source of lhigher pressure con- Y struction of student pilots, the combination of an equalizer tank having a controlled variable pressure potential, an instrument Yfor indicating assumed altitude changes connected to said tank, said instrument being responsive to the `pressure within said tank, a source of higher air pressure connected with said tank, a valve interposed between said tank and said source of higher Vair pressure, and meansassociated with said valve forcausing a uniform flow from said source of higher air pressure to said tank for a given valve opening regardless of the pressurediiferential between said source ofY higher air pressure and said equalizer tank.

9. InV argrounded aviation trainer for the instruction of student pilots, the combination of a throttle, an equalizer tank having a controlled variable pressure potential, an instrument for indicating assumed altitude changes connected to said tank, said instrument being responsive to the pressure within said tank, a source of higher pressure connected with said tank, a valve interposed between said tank and said source of higher pressure, said valve being responsive to the setting of said throttle, and means associated with said valve for causing a uniform flow from said source of higher pressure to said equaliz'er tank for a given valve opening regardless of the pressure diierential between said tank and'said source of higher pressure.

10. In a grounded aviation trainer having a fu- Y selage capable ofV pitching in simulation of theV climbing and diving of a plane in actual night the combination of an equalizer tank -having a controlled variable pressure potential, an instrument for indicating assumed altitude changes connected to said tank, said instrument being `responsive to the pressure within said tank, a

source of higher pressure connected with said tank, a valve interposed between said tank and said source of higher pressure, saidV valve being `Vresponsive to the pitching of said fuselage, and

means associated with said valve for causing a uniform flow from said source of higher pressure to said equalizer tank for a given valve opening regardless of the pressure differential between changes connected to said tank, said instrument being responsive to the pressure within said tank, a source of higher pressure connected with said tank, a Vvalve interposed between said tank and said source of higher pressure, said valve being responsive to the pitching of said fuselage as well as to the setting of said throttle,'and means associated with said valve for'causing a uniform l2. In a grounded aviation trainer for the instruction of student pilots the combination ofvan equalizer tank having a controlled variable pressure potential, an instrument for indicating assumed altitude changes connected to saidptank, said instrument being responsive` to the pressure within said tank, a source of pressure connected with said tank, said source of pressure having a potential normally different from the pressure withinsaid tank, a valve interposed between said tank and said source of pressure, and means associated with said valve, and operable within predetermined limits, for causing a uniform flow through said valve for a given valve opening regardless of the difference in the pressures within said pressure containing members.

13. In a grounded aviation trainer for the instruction of student pilots the combination of an equalizer tank having a controlled variable pressure potential, an instrument connected to said tank, said instrument being responsive to the pressure within said tank, a source of lower air pressure connected with said tank, a valve interposed between said tank and said source of lower air pressure, and means associated with said valve for causing a uniform flow `from said equalizer tank to said source of 'lower air pressure for agiven valve opening regardless of the Y pressure differential therebetween.'

"` able within predetermined limits, for causing a uniform flow from said equalizer tank to said source of lower air lpressure for a given valve opening regardless of the pressure differential between said tank and said source of lower air pressure, and within other predetermined limits a now dependent upon the pressure differential between said equalizer tank` and said source of lower air pressure,

l5. In a grounded aviation trainer for the instruction of student pilots the combination of an equalizer tank having a controlled' variablepressure potential, a source of normally higher air pressure connected with said tank, a valve interposed-between said tank and said source of higher air pressure, and means associated with ,said

valve, and operable within predetermined limits, for causing a uniform-now from said source of higher air pressure to said tank for a given valve opening'Y regardless of theV pressure differential therebetween.

16. In a grounded aviation trainer for the invalve, and operable within predetermined limits,

flow from said source of higher' pressureV to said f equalizer Ytank for a given valve opening regardless ofthe pressure differential therebetween.

for causing a uniform flow from said source. of

higher air pressure to said tank for a given valve Y openingV regardless of the pressure differentialassume sure, potential, a source ofv lowerv pressure, and a of the pressure differential between saidtank and each of said sources. y

` 18, In a groundedaviation trainer for theinstruction of' student .pilots the combination, of.' an equalizer tank having a controlled variablek pressure potential, an instrument connectedto 'said tank, said instrument beingV responsive ,to the pressure within said tank,y a source of lower pressure andav source of higherpressure, each'off'said sources being connected' with saidtank,A a valve interposed between saidtank and said source of lower pressure, and a valveinterposed between said tank and said source of higher pressure,and means associated with each of said valves, and operable within predetermined limits, for causa,- ing a uniform now through each of said valves for a given valve opening regardless of the, pressure differential between, saidl tank and each of said sources.

19. In a grounded aviation trainer for the instruction of student pilots the combination often equalizer tank having a controlled variable pres*- sure potential, a source of lower air pressure and av source of higher air pressure, each of said f sources being connected with said tank, a, valve interposed between said tank and said sourcey of lower air pressure and a valve interposed between said tank and said source of higher air pressure, and means associated with each ofv said valves,

and operable within predeterminedy limits', for

causing a uniform flow through each of saidivalves for a given valve opening regardless of' the pres;- sure differential between said tank and each of said sources of' pressure, and within other predetermined limits, a ow dependent upon the pressure diiierential between said tank and each of said sources of air pressure.

20. In a grounded aviation trainer for the instruction of student pilots the combination of a throttle, an equalizer tank having a controlled variable pressure potential, a source of lower pressure and a source of higher pressure, each of said sources being connected with said tank, a valve interposed between said tank and said source of lower pressure, and a valve interposed between said tank and said source of higher pressure, each of said valves being responsive to the setting of said throttle, and means associated with each of said valves, and operable within predetermined limits, `for causing a uniform flow through each of said valves for a given valve opening regardless of the pressure differential between said tank and each of said sources.

21. In a grounded aviation trainer having a fuselage capable of pitching in simulation of the climbing and diving of a plane in actual flight v the combination of an equalizer tank having a controlled variable pressure potential, a source of lower pressure and a source of higher pressure, each of said sources being connected with said tank, a. valve interposed between said tank and said source of lower pressure, and a valve interposed between said tank ,and said source of higher pressure, each of said valves being responsive to the pitching of said trainer fuselage, and

means associatedl with each of said valves, and operablewithin predetermined limits, for causing aiunifornr ow'through each of `SaidfvaIVes for a fgivenk valve openingf regardless of the pressure diiferentia'l between-said tank andi eachy of? said sources. f f f y 2,21' In a groundede aviation"trainerforfthe instruction; ofA student; pilots theA combinationfof" an 'equalizertank havingv a controlledvariable-,- pressure potential; a source voflower pressure and a source of higher pressure;A each` vofO said sources beingconnected with said;` tank, yavalve interposed between said equalizerA tank andY said source of lowerpressuredandal valve interposed between said equalizer tank and saidy sourcev of higher pressure, andv a pressurer regulator associated'witheach or said-v valves, and operable within predetermined; lin'iits',k for causingfr a; unifornr'ow through'eachof-"saidr valvesfor agiven 'valveopening;` regardlessof the pressurediierential-between saidtankandY ea-chof' said sources;

l23. In a grounded aviation trainer for the instruction of;l` studentpilots the combination of an equalizerY tankhavingr a cont-rolledvariablepressurepotential, an instrument-connected withpand being responsiveto the-pressure within said tank, a; source oflower'pressure anda source" of higher pressure, ,each ofsaid sources beingV connected with saidj tank, ai valve interposed betweenl` said tankV and; said? source ofr'flower pressure, anda valve interposed between saidA tank-l and) said sourcey offhilgher pressure, j andl a pressure regulater; associated" with` each Yofi said` valves, andY operable within predeterminedlimits, for causing a uniform flow through, each ofi said valves for a givenl valve' openingI regardlessof the presdifferential` between saidtankand each of said sources; i

24; Ina grounded aviation trainer for theinstruction Vofr student, pilots the combination ofv a throttle,l an equalizerV tankhaving a controlled variable pressure` potential, a sourcev of ylower 'pressure and a source ofhigher' pressure, each of said sources being connected:` with said tank, a valve interposed between said tank and said source of lower pressure, and a valve interposed between said tank and said source of higher pressure, each of said valves being responsive to the setting of said throttle, and a pressure regulator associated with each of said valves, and operable within predetermined limits, for causing a uniform ow through each of said valves for a given valve opening regardless of the pressure differential between said tank and each of said sources.

25. In a grounded aviation trainer having a fuselage capable of pitching in simulation of the climbing and diving of a plane in actual flight the combination of an equalizer tank having a controlled variable pressure potential, a source of lower pressure and a source of higher pressure, each of said sources being connected with said tank, a valve interposed between said tank and each of said sources, each of said valves being responsive to the pitching of said trainer fuselage, and a pressure regulator associated with each of said valves, and operable within predetermined limits, for causing a uniform flow through each of said valves for a given valve opening, regardless of the pressure diiierential between said tank and each of said sources.

26. In a grounded aviation 'trainer for the instruction of student pilots the combination of an equalizer tank having a controlled variable pressure potential, a source of lower air pressure, a valve having one port connected to said fio 'ftank, a pressure iregulator between the second pressure differential across the ports port 'of said valve and said source of lower air pressure, said pressure regulator comprising va three-portvalve, one ofgsaid ports being `connected to the second port of said rst-mentioned valve, the second of said ports being 'connectedl to saidsource of lower air pressure and the-last of said :portsbeing Vin communication with the atmosplfngije,4 and pressure-responsive means for placing the rst-mentioned .port ofsaid threeportvalve in communication with either. of the othertwo ports in order to maintain thev desired of said firstmentioned valve.- Y i .Y

aviationtrainer forthe instruction of student'pilots the combination of van equalizentank having a controlled variable. pres- Y sure potentiaha source of .lower pressure anda `source of normally higher. pressure, a valve hav,- ing oneport connected to said tank, and a pressure regulator between the second port of said valve and said source of normally higher pressure, s aidpressure regulator comprising a, threeport valve, one ofy said ports being connected to the second port of said mst-mentioned valve, the

second of said V.ports. b'f zing vconnected to said sourcebf Vlower pressure,and the lastoi said portsbeing connected to said source `of normally higher pressure, and pressure-responsive means 'Y for placing the :firstmentioned port of said three-port valve in communication with either of the otherrtwo ports in order to maintain the. desired pressure differential across the ports'of said n rstmentioned'valve. Y

28. In a grounded aviation trainer for' the vini struction of student pilotsthe combination of an equalizer tank having a controlled variable presnication with said equalizer tank, a spring of pre- VVdetermined strength interposed between .the

movable end of said other bellows and the housmovable rend of said beiiws and the 'housing 0f said valve, one of the ports of said. three-port valve being in communication .with said other bellows, the second of said ports 'being in communication with a source of lower pressure, and the last fof said portsl being in communication with the atmosphere, the relative pressures Within said bellows and the strength of said spring determining.'with which, if either, of said last two ports said first-mentioned port is in communication.

29, In a grounded aviation trainer for the in` struction of student pilots the combination of an equalizer tank having a controlled variable pres'- sure'pote'ntiaha three-port slide valve, a pair of collapsible bellows .eachrhaving itsimov'able Yend attached tothe opposite ends of the slide of said slide valve, one of said bellows being Yin commuing of said valve, one of the ports of said threeport valve being in communication with saidV last-mentioned bellows, the second of said ports being in communication with a source ofV lower pressure, and the last of said ports being in communication with a source of pressure normally higher than that within said tank, the relative pressures within said bellows and the strength of said spring determining .with which, if either, of said last two ports saidrstmentioned port is in communication.

V30. In a grounded aviation trainer for the in.- struction of student pilots the combination of an equalizer tank having a vcontrolled variable pressure potential; a source of highery pressure connect'ed with said equalizer tank, a valve interposed between said tank and said source of higher, pressure, and a bleed hole associated with said pressure source for allowing' atmosphere to entersad tank when said pressure source isin- -terrupted and said Valve is open.

GUNNE LOWKRANTZQ 

